This invention relates to a vehicle-mounted electrical junction box and more particularly relates to a vehicle-mounted electrical junction box that can reduce heat generation in a circuit board and downsize the circuit board by intensively arranging relays and fuses, which are mounted on embodiments of an electrical junction box and are heat-generating parts, near a side of the circuit board to simplify an internal circuit.
Generally, a number of relays and fuses are mounted on an electrical junction box that distributes electrical power to electrical devices mounted on a motor vehicle, such as an automobile.
FIG. 5 shows an example of electrical junction box disclosed in JP 2005-302330A. The electrical junction box 1 includes a casing comprising a first casing member 2 and a second casing member 3. A relay module 4 is disposed on a central position in the casing. A fuse module 5 and connector modules 6, 7 are disposed on an outer peripheral position of the casing to surround the relay module 4. An electric control unit (“ECU”) 8 is disposed on the central position of the casing above the relay module 4 while an internal circuit body 9 is disposed below the relay module 4.
In the electrical junction box 1 of JP 2005-302330A, a circuit interposing the relays and fuses distributes an electrical current, which is applied from the connector module 6 to an external circuit via the relay module 4, the fuse module 5, and the internal circuit body 9 (or the ECU 8). Because the circuit extends between the central and outer peripheral positions of the casing in order to interpose the relays and fuses, the circuit extends for a long distance, the amount of heat generated increases, and the size of the circuit board required is increased.
Additionally, because the relay module 4 is disposed between the ECU 8 and the internal circuit body 9 in a vertical direction, generated heat is likely to accumulate in the casing, and consequently the interior of the casing tends to overheat.
Furthermore, another drawback of the conventional electrical box is inefficient use of space. For example, as shown in FIG. 6, first and second spaces S, which are above and below the fuse module 5 disposed on the outer peripheral position of the casing, become dead spaces, thereby increasing the size of the conventional electrical junction box.